Australian Agriculture Department officials have estimated that nearly half of all imported raw prawns were infected with white spot disease before imports were suspended in January.

The officials told a Senate Estimates hearing in Canberra on Wednesday that six importers supplied "the vast majority" of the contaminated prawns.

The Department has since revoked their import permits and approvals.

"We have made a referral to the CDPP [Commonwealth Director of Public Prosecutions], to pursue charges and further referrals are being considered," the Department's head of biosecurity, Lyn O'Connell, told Estimates.

Biosecurity officials seized almost a tonne of meat from international travellers at Queensland's Gold Coast airport in 2016, as passengers increasingly fail to adhere to Australian restrictions on food entering the country.

The Agriculture Department has revealed that more than 6,700 contraband food items were collected at the Gold Coast airport alone in 2016.